Is 4D printing the next step?

3D printing, entering a new dimension

By Peter Feuilherade

3D printing, also known as additive manufacturing, is the computer-controlled sequential layering of materials to create three‑dimensional shapes. Originally developed more than 30 years ago, it is only in recent years that applications of the technology have expanded in fields as diverse as aerospace, medicine and dentistry, construction, the automotive industry and clothing and footwear.

EDAG Genesis 3D-printed concept car (Photo: Photo: EDAG Group)

The main 3D printing technologies include Fused Deposition Modelling (FDM: melting of thermoplastic material by heating and then extruding it to create an object layer by layer), Selective Laser Sintering (SLS: using a high power carbon dioxide laser to fuse small particles of metal or plastic powder into 3D objects), Electron Beam Melting (EBM: using a cathode ray as a heat source to melt metal powder in a high vacuum, layer by layer, to create a product) and Stereolithography (SLA: producing 3D models layer by layer by curing a photo-reactive resin with a UV laser).

The additive nature of 3D printing helps in reducing wastage of materials and the associated costs. It now has a growing range of uses beyond rapid prototyping. Although 3D printers are still not cost-effective for most high-volume commercial manufacturing, they are faster and easier to use than they were, and can handle multiple materials. The expiry of key patents has allowed many small companies to produce cheap desktop 3D printers aimed at consumers.

A number of IEC Technical Committees (TCs) and Subcommittees (SCs) develop and coordinate International Standards covering the safety aspects of 3D printing and the electric and electronic components and technology used in additive manufacturing equipment.

Research is now under way on the next stage, dubbed “4D printing”, which involves the use of 3D-printed objects and materials able to change shape over time when immersed in liquids or exposed to external energy sources.

Print-a-part

In 2015, 90% of 3D printing applications in the automotive industry were for prototyping and only 10% for production. However, the technology is starting to spread, and is used not just for design but also for manufacturing, repair and replacement.

Start-up companies in the US have already produced prototype 3D‑printed cars comprising a mix of carbon fibre and thermo-plastic modular body parts with original equipment manufacturer (OEM) components such as the engine and drive train. In the collision repairs sector, 3D printing could speed up work by allowing the printing on site of many small parts, sometimes for cars that are no longer manufactured.

According to a January 2016 report by the US consultancy Frost & Sullivan, the application scope of 3D printing is currently restricted to the production of extremely low volume parts and production tooling. Despite this, the firm forecasts that the technology will generate USD 4,3 billion in the automotive industry by 2025, and achieve deeper penetration in production and the aftermarket.

“3D printing technology will allow OEMs and suppliers to print at multiple locations, thereby diminishing waiting periods and overall costs. Ultimately, this technology will also enable users to design and print customized parts, in line with each customer’s requirements,” the Frost & Sullivan report predicts.

Out of this world

Aerospace is another sector where 3D printing has made great advances. Since 2015, astronauts aboard the International Space Station have created 3D‑printed replacement parts on demand. In January 2016, Boeing reported the successful maiden flight of its latest‑generation 737 MAX aircraft, powered by the world’s first jet engines to include 3D-printed fuel nozzles, while another US company successfully tested a 3D-printed hypersonic scramjet engine combustor made by an additive manufacturing process known as Powder Bed Fusion (PBF). The European consortium Airbus has said it plans to 3D‑print 10% of all aircraft parts in the near future, citing the technology’s production efficiencies and aircraft weight reduction as reasons for its adoption.

IEC TC 17: Switchgear and controlgear, and TC 121: Switchgear and controlgear and their assemblies for low voltage, and their SCs, prepare International Standards on switches and relays. TC 2: Rotating machinery, is responsible for Standards covering the servo and stepper motors used to move extrusion heads or sintering lasers. TC 96: Transformers, reactors, power supply units, and combinations thereof, deals with Standards relating to power supplies.

IEC TC 76: Optical radiation safety and laser equipment, is the leading body on laser standardization, including the high-power lasers used to manufacture components using metal powders.

The construction industry has adapted 3D printing technologies to create buildings and other structures. Researchers at the Massachusetts Institute of Technology are investigating a variety of 3D printing systems for construction, including one which uses swarms of small robots that extrude fast-setting materials to fabricate large structures.

A Chinese company has used large 3D printers spraying a mixture of quick drying cement and recycled raw materials to construct 10 small demonstration ‘houses' in less than 24 hours, comprising pre‑fabricated sections joined together with steel reinforcing bars. And an Italian research group has created a giant printer 12 metres high that can 3D‑print huts using clay. Its main goal is to provide shelter in desert regions such as North Africa, where it has printed its first structures. The US space agency NASA, meanwhile, is looking at ways in which robotic 3D printers using material from the surfaces of the Moon and Mars could construct 3D-printed buildings and other infrastructure such as landing pads.

Best foot forward

Several of the most significant deployments of 3D printing technology have been in medical applications. 3D printing has enabled the production of customized hearing aids and bacteria‑resistant dentures, while the first 3D hip implants and knee replacements have resulted in improved healing times and functioning of the implants. 3D technology can print patient‑specific models of organs or body parts from medical scans for use in planning and practising difficult surgical operations, or produce prosthetic limbs at low cost for people in less developed countries who previously had no access to such life-altering devices.

Titanium is non-toxic and the strongest metal that can currently be used in 3D printing. It has been used to produce 3D‑printed prostheses ranging from a metacarpal thumb bone to hip joints and even an entire sternum and ribcage. Customized synthetic bone implants made in part from the same minerals found in natural bone material can also be 3D printed to help patients recovering from bone loss. As the natural bone grows back, the implants dissolve harmlessly in the patient’s body.

In 2015 the US Food and Drug Administration for the first time approved the use of 3D printing in the manufacture of medicines, paving the way for the potential customization of the size, dose, appearance and rate of delivery of drugs to suit the needs of individual patients and make them safer and more effective.

In the rapidly developing field of biofabrication, a research team at Heriot‑Watt University in Edinburgh has developed a 3D printer to bioprint stem cells from an adult patient’s own cells, which are capable of developing into almost any other cell in the body. Initially, they plan to use the cell printing process to make miniature 3D human tissues for testing pharmaceutical drugs. Looking ahead, 3D printing of body parts, organs and living tissues for human transplant may become a reality.

Several IEC TCs and their SCs are responsible for the safety aspects of the growing use of 3D printing for medical applications such as the preparation of anatomical models, customized implants and bioprinting. They include TC 119: Printed electronics, and TC 62: Electrical equipment in medical practice, and its SCs, which prepare International Standards and other publications covering “electrical equipment, electrical systems and software used in healthcare and their effects on patients, operators, other persons and the environment".

The research and consultancy company IDTechEx forecasts that the total 3D printing market will reach USD 20 billion by 2025, with the bioprinting market accounting for more than USD 4 billion. “The trillion dollar oil and gas industry is an emerging user of 3D printing with the highest forecast growth followed by the more established aerospace industry,” IDTechEx adds.

International Data Corporation (IDC), a global market intelligence provider, predicts an even higher growth rate within the next three years alone, based on greater mainstream adoption. According to IDC research published in January 2016, global spending on 3D printing will grow at a compound annual growth rate (CAGR) of 27% from nearly USD 11 billion in 2015 to USD 26,7 billion in 2019. Most of the growth is expected from markets in the US, Western Europe and Asia, as China in particular becomes a leading market for 3D printing hardware and services.

Shape shifting and the fourth dimension

The next few years will see rapid advances in metal 3D printing to produce a wider range of finished goods, including more medical implants than is possible today. The speed of printers is expected to increase. Research is underway on how to combine different types of materials such as metals and plastics in a single build cycle, and how to embed components such as sensors, electronics and batteries.

The emerging technology of 4D printing brings exciting possibilities. 4D printing involves the use of shape-shifting materials, where the fourth dimension relates to the time taken for self‑transformation. These programmable or ‘smart’ materials can adapt their properties and shape on demand after 3D printing, when immersed in water or exposed to external sources of energy such as heat, current or light. Potential applications include tissue engineering and medical implants that change their shape inside the body.

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